1. Field of the Invention
The present invention relates to a resistive touch panel.
2. Description of the Related Art
Control input devices including a touch panel are widely used. FIG. 1 is a diagram illustrating the structure of a typical resistive touch panel 1 (hereinafter referred to as a “touch panel”). A resistive layer 11 is bonded to one side of a film 10. A force can be applied to the other side of the film 10 by a finger 3, a stylus pen (not illustrated), or other means. A resistive layer 12 is bonded to one side of a glass panel 13. In the touch panel 1, spacer dots 14 are interposed between the two resistive layers 11, 12 to space the resistive layers 11, 12 apart from each other. Under the touch panel 1 is disposed a liquid crystal display (LCD) 4.
When a force is applied to the top side of the touch panel 1 (to the film 10) by the finger 3, a stylus pen, or other means, the two resistive layers 11, 12 under applied voltage become shorted to each other, and by measuring the voltage values at the touched location with a touch panel controller, the coordinates of the touched location can be determined.
The spacer dots 14 are provided to prevent inadvertent contact between the two resistive layers 11, 12 due to external factors such as the environment. Conventional touch panels 1 are not configured to differentiate the touch sensitivity in one or more regions from that in the remaining regions. A device for sensing the pressing force may be usable but it cannot by itself alter the pressing force to the touch panel (Japanese Patent Laid-Open No. 2013-127690).
When a touch panel is used for operation of a machine tool, responsivity to a light touch is desired for use in character entry and button operations (including tapping, rotation, enlargement and reduction operations).
On the other hand, when a touch panel is employed for a machine tool control panel, which includes buttons for actually activating the machine, it is necessary to prevent accidents due to malfunction of the machine. Thus, it is desired that the buttons for actually activating the machine do not respond to a light touch but respond to a somewhat heavy touch.